Structural links between zeolite‐type and clathrate hydrate‐type materials: Synthesis and crystal Structure of [N(CH 3 ) 4 ] 6 [Al x Si 8−x O 18−x (OH) 2+x ] · 44H 2 O (x = 3–4)

A novel tetramethylammonium aluminosilicate hydrate with the approximate composition [NMe 4 ] 6 [Al x Si 8−x O 18−x (OH) 2+x ] · 44H 2 O (x = 3–4) has been identified by powder X‐ray diffraction as a component in a polyphasic solid mixture which crystallized at room temperature from an aqueous NMe 4 OHAl 2 O 3 SiO 2 solution. Large crystals of the novel hydrate phase could be mechanically selected from that mixture. The crystal structure has been determined from 1 196 unique MoK α diffraction data measured at 180 K: Tetragonal crystal system, cell constants a = 16.181(4) and c = 17.450(4) Å, space group P4/mnc with Z = 2 formula units per unit cell, R = 0.072. The host‐guest compound is of polyhedral clathrate type with a mixed three‐dimensional, (mainly) four‐connected network composed of oligomeric aluminosilicate anions [Al x Si 8−x O 18−x (OH) 2+x ] 6− and H 2 O molecules linked via hydrogen bonds OH … O. The aluminosilicate anions possess a cube‐shaped (double four‐ring) structure. Orientationally disordered cationic guest species NMe 4 + are enclosed in the large [4 6 6 8 ] and [4 1 5 10 6 7 ] polyhedral voids of the host framework; the small [4 6 ] cages (i.e. the double four‐ring anions) and [4 3 5 6 ] cages are empty. The hydrate is a further member in a recently discovered series of clathrates with mixed tetrahedral networks, which provides a structure‐chemical link between zeolite‐ and clathrate hydrate‐type host‐guest compounds.